Question

在这段代码中，我面临着滞后的问题和高CPU使用率。我创建了三个差异文件。

第一个DrawView.swift

class DrawView: UIView {

var lines: [Line] = []
var firstPoint: CGPoint!
var percentageOfXY:[String]=[]
var viewWidth:CGFloat!
var viewHeight:CGFloat!
var drawColor:UIColor!

override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {

    viewWidth = frame.width
    viewHeight = frame.height
    let touch = touches.first as UITouch?
    let start = touch!.locationInView(self)
    let percentageX = round(((start.x)*100)/viewWidth*100)/100
    let percentageY = round(((start.y)*100)/viewHeight*100)/100
    firstPoint = CGPointMake(percentageX, percentageY)
}
override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {

    viewWidth = frame.width
    viewHeight = frame.height
    let touch = touches.first as UITouch?
    let curr = touch!.locationInView(self)
    let percentageX = round(((curr.x)*100)/viewWidth*100)/100
    let percentageY = round(((curr.y)*100)/viewHeight*100)/100
    let lastPoint = CGPointMake(percentageX, percentageY)
    lines.append(Line(start: firstPoint, end: lastPoint, color: drawColor))
    firstPoint = lastPoint
    self.setNeedsDisplay()

}
override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?)
{

}
override func drawRect(rect: CGRect) {

    for line in lines
    {
        let context = UIGraphicsGetCurrentContext()
        CGContextSetLineCap(context, CGLineCap.Round)
        CGContextSetLineWidth(context,3)
        let startX = ((line.start.x)*viewWidth)/100
        let startY = ((line.start.y)*viewHeight)/100
        let endX = ((line.end.x)*viewWidth)/100
        let endY = ((line.end.y)*viewHeight)/100
        CGContextBeginPath(context)
        CGContextMoveToPoint(context, startX,startY)

        CGContextAddLineToPoint(context, endX,endY)
        CGContextSetStrokeColorWithColor(context,line.color.CGColor)
        CGContextStrokePath(context)

    }
}
}

第二个用于以格式存储坐标的Line.swift。

class Line 
{
var start: CGPoint!
var end: CGPoint!
var cord: [String]!
var color:UIColor!
init(start _start: CGPoint,end _end: CGPoint,color _color:UIColor)
{
    start = _start
    end = _end
    color = _color
}
}

第三个用于颜色选择。

@IBOutlet weak var drawView: DrawView!
override func viewDidLoad() {
    super.viewDidLoad()
    drawView.backgroundColor = UIColor.clearColor()
}

@IBAction func redColor(sender: AnyObject) {
    let theDrawView = drawView as DrawView
    var color:UIColor!
    color = UIColor.redColor()
    theDrawView.drawColor = color
}
@IBAction func greenColor(sender: AnyObject) {
    let theDrawView = drawView as DrawView
    var color:UIColor!
    color = UIColor.greenColor()
    theDrawView.drawColor = color
}
@IBAction func blueColor(sender: AnyObject) {
    let theDrawView = drawView as DrawView
    var color:UIColor!
    color = UIColor.blueColor()
    theDrawView.drawColor = color
}

在这个我画画中，但是通过滞后的问题它画出直线。

Answer 1

几个问题：

从你的循环中获取UIGraphicsGetCurrentContext。
从你的循环中获取CGContextSetLineCap。
从循环中获取CGContextSetLineWidth。
完全杀死CGContextBeginPath - CGContextStrokePath会为你做这件事。
您应该发明一个带有点数组的线对象，这样您就不必为每个小段设置颜色。 TouchesBegan..TouchesEnded将开始并完成其中一个线对象。（如果允许多点触控，你必须更加小心，但它看起来不像你。）
如果您修复上面的线对象，您将拥有一对嵌套循环。然后你将CGContextMoveToPoint移出内循环的前面，CGContextSetStrokeColorWithColor和CGContextStrokePath移出内循环的末尾。

但是现在你的真正问题是：在屏幕上移动手指很容易就能产生每秒几千个像素的交叉点。你的touchesMoved每秒只能被调用60次（更常见的是在iPad Pro上）。如果您希望草图看起来平滑，则必须“弥补”从未提供过的数据。请参阅维基百科上的Kochanek-Bartels或Catmull-Rom splines。

使用swift 2在ios 8.4中连续绘制期间消除滞后延迟

1 个答案: